The present patent application relates to thickening water-in-oil latices, to a process for their preparation and to their use as thickeners and/or emulsifiers for skincare and haircare products or for the manufacture of cosmetic, dermopharmaceutical or pharmaceutical preparations.
Various thickeners exist and are already used for these purposes. Natural products such as guar gums or starch are known in particular, but the drawbacks thereof are those inherent in natural products, such as currency fluctuations, difficulties in supply and a random quality.
Synthetic polymers in powder form, mainly polyacrylic acids, are also widely used but have the drawback of requiring neutralization during use, since they only develop their viscosity from a pH of greater than 6.5 and they are often difficult to dissolve.
Synthetic thickening polymers which are in the form of reverse latices, i.e. latices in which the continuous phase is an oil, also exist. These latices dissolve extremely quickly; the polymers contained in these reverse latices are usually acrylamide/alkali metal acrylate or acrylamide/sodium 2-acrylamido-2-methylpropanesulphonate copolymers; they are already neutralized and, when dissolved in water, for example to a concentration of 1%, it is observed that the pH is generally greater than 6.
However, acrylamide/sodium acrylate copolymers do not develop considerable thickening properties when the pH is lowered below 6; on the other hand, the acrylamide/sodium 2-acrylamido-2-methylpropane-sulphonate copolymers described in EP 0 503 853 conserve considerable thickening capacity even at a pH equal to 4.
However, such copolymers have monoacrylamide contents which, although extremely low, may lead in the future to their use in cosmetics not being possible, on account of the changes in European regulations regarding hazardous substances.
Furthermore, all of the polymers mentioned have a tendency to lose their thickening property when the medium to be thickened, for example a cosmetic product, contains salts; this tendency becomes accentuated as the concentration of salts present in the said medium increases.
The Applicant has thus become interested in the search for novel acrylamide-free reverse emulsions which are more stable with respect to electrolytes.
According to a first aspect of the present invention, its subject is the use of a composition comprising an oil phase, an aqueous phase, at least one emulsifier of water-in-oil (W/O) type and at least one emulsifier of oil-in-water (O/W) type, in the form of a reverse latex comprising from 20% to 70% by weight, and preferably from 25% to 40% by weight, of an anionic polyelectrolyte, the said anionic polyelectrolyte being based on partially neutralized acrylic acid, which may be branched and/or crosslinked, to prepare a cosmetic, dermopharmaceutical or pharmaceutical composition.
The expression xe2x80x9cemulsifier of water-in-oil typexe2x80x9d denotes emulsifiers with an HLB value which is low enough to give water-in-oil emulsions, such as the surfactant polymers sold under the name Hypermer(trademark) or such as sorbitan esters, for instance sorbitan monooleate sold by the company SEPPIC under the name Montane(trademark) 80 or sorbitan isostearate sold by SEPPIC under the name Montane(trademark) 70.
The expression xe2x80x9cemulsifier of the oil-in-water typexe2x80x9d denotes emulsifiers with an HLB value which is high enough to give oil-in-water emulsions, such as, for example, ethoxylated sorbitan esters, for instance sorbitan oleate ethoxylated with 20 mol of ethylene oxide or sorbitan laurate ethoxylated with 20 mol of ethylene oxide, sold by the company SEPPIC under the names Montanox(trademark) 80 and Montanox(trademark) 20, respectively, castor oil ethoxylated with 40 mol of ethylene oxide or alternatively lauryl alcohol ethoxylated with 7 mol of ethylene oxide, sold by the company SEPPIC under the names Simulsol(trademark) OL 50 and Simulsol(trademark) P7, respectively.
The expression xe2x80x9cpartially neutralized acrylic acidxe2x80x9d denotes more particularly acrylic acid partially salified in the form of an alkali salt, such as the sodium or potassium salt, or in the form of the salt of a nitrogenous base, such as the ammonium salt, or a salt with a compound containing quaternary ammonium, such as an amino alcohol salt. It is preferably acrylic acid partially neutralized in the form of the ammonium salt (NH4+) or a monoethanolamine salt (HOCH2CH2NH3+).
The expression xe2x80x9cbranched polymerxe2x80x9d denotes a non-linear polymer which contains pendant chains so as to obtain, when this polymer is dissolved in water, a strong state of entanglement leading to very high low-gradient viscosities.
The expression xe2x80x9ccrosslinked polymerxe2x80x9d denotes a non-linear polymer which is in the form of a three-dimensional network which is insoluble in water but swellable in water and thus leads to the production of a chemical gel.
The composition according to the invention can comprise crosslinked units and/or branched units.
The term xe2x80x9camino alcoholxe2x80x9d means mono- or poly(hydroxyalkyl)amines.
A subject of the invention is, more particularly, the use, as defined above, of a composition in which the anionic polyelectrolyte is crosslinked and/or branched with a crosslinking agent and/or a branching agent chosen from trimethylolpropane triacrylate, ethylene glycol dimethacrylate or methylenebis(acrylamide) or compounds comprising at least two allyl radicals such as, for example, diallyloxyacetic acid or a salt thereof such as sodium diallyloxyacetate, triallylamine or diallylurea.
The crosslinking and/or branching agent is generally used in a molar proportion, expressed relative to the monomers used, of from 0.05% to 0.5% and preferably from 0.1% to 0.25%.
The latex according to the invention generally contains from 2.5% to 15% by weight and preferably from 4% to 9% by weight, of emulsifiers, among which from 20% to 50%, in particular from 25% to 40%, of the total weight of the emulsifiers present are of the water-in-oil (W/O) type and in which from 80% to 50%, in particular from 75% to 60%, of the total weight of the emulsifiers are of the oil-in-water (O/W) type.
According to one specific aspect of the present invention, the oil phase of the composition used represents from 15% to 40%, preferably from 20% to 25%, of the total weight of this composition.
This oil phase consists either of a commercial mineral oil containing saturated hydrocarbons of paraffin, isoparaffin or cycloparaffin type, with a density at room temperature of between 0.7 and 0.9 and a boiling point of greater than 180xc2x0 C., such as, for example, Exxol(trademark) D 100 S sold by Exxon or a white mineral oil such as Marcol(trademark) 52 also sold by Exxon, the isohexadecane sold by Bayer or isododecane, or of a plant oil such as hexamethyltetracosane or squalane, or of a synthetic oil such as polyisobutene or hydrogenated polyisobutene, or of a mixture of several of these oils.
The isohexadecane, which is identified in Chemical Abstracts by the number RN=93685-80-4, is a mixture of C12, C16 and C20 isoparaffins containing at least 97% C16 isoparaffins, among which the main constituent is 2,2,4,4,6,8,8-heptamethylnonane (RN=4390-04-9). It is sold in France by the company Bayer. Marcol(trademark) 52 is a commercial oil corresponding to the definition of liquid petroleum jellies in the French Codex. It is a white mineral oil in accordance with the rules FDA 21 CFR178.878 and CFR 178.3620(a); it is registered in volume US XXIII of the USA Pharmacopoeia (1995) and in the European Pharmacopoeia (1993).
According to one preferred aspect of the present invention, the oil phase of the composition used comprises isohexadecane or a white mineral oil.
The latices contain between 20% and 50% water. They can also contain various additives such as complexing agents, transfer agents or chain-limiting agents.
According to a second aspect of the present invention, its subject is a composition as employed in the use defined above, comprising an oil phase, an aqueous phase, at least one emulsifier of water-in-oil (W/O) type and at least one emulsifier of oil-in-water (O/W) type, in the form of a reverse latex comprising from 20% to 70% by weight, and preferably from 25% to 40% by weight, of a crosslinked anionic polyelectrolyte, the said anionic polyelectrolyte being based on partially neutralized acrylic acid, characterized in that the crosslinking agent is chosen from compounds comprising at least two allyl radicals and most particularly from diallyloxyacetic, sodium diallyloxyacetate or triallylamine.
According to a third aspect of the present invention, its subject is a composition as employed in the use defined above, comprising an oil phase, an aqueous phase, at least one emulsifier of water-in-oil (W/O) type and at least one emulsifier of oil-in-water (O/W) type, in the form of a reverse latex comprising from 20% to 70% by weight, and preferably from 25% to 40% by weight, of an anionic polyelectrolyte which may be branched and/or crosslinked, characterized in that the said anionic polyelectrolyte is based on partially neutralized acrylic acid, in the form of an amino alcohol salt, and preferably a monoethanolamine salt.
According to a fourth aspect of the present invention, its subject is also a process for preparing the composition as defined above, characterized in that:
a) an aqueous solution containing the monomers and the optional additives is emulsified in an oil phase in the presence of one or more emulsifiers of water-in-oil type,
b) the polymerization reaction is initiated by introducing a free-radical initiator and optionally a co-initiator into the emulsion formed in a), after which the reaction is left to proceed,
c) when the polymerization reaction is complete, one or more emulsifiers of oil-in-water type are introduced at a temperature below 50xc2x0 C.
According to one variant of this process, the reaction medium obtained from step b) is concentrated by distillation before step c) is carried out.
According to a preferred embodiment of the process as defined above, the polymerization reaction is initiated by a redox couple which generates hydrogen sulphite ions (HSO3xe2x88x92), such as the cumene hydroperoxide/sodium metabisulphite (Na2S2O5) couple the sodium, potassium or ammonium peroxydisulphate/sodium metabisulphite or the cumene hydroperoxide/thionyl chloride (SOCl2) couple, at a temperature below or equal to 10xc2x0 C., if desired accompanied by a polymerization co-initiator such as, for example, azobis(isobutyronitrile), followed by proceeding either under virtually adiabatic conditions up to a temperature of greater than or equal to 50xc2x0 C., or by controlling the temperature.
A subject of the invention is also a cosmetic, dermopharmaceutical or pharmaceutical composition, characterized in that it comprises at least one reverse latex as defined above, as well as a process for preparing a cosmetic, dermopharmaceutical or pharmaceutical composition, characterized in that from 0.1% to 1% by weight of a composition whose use is the subject matter of the present invention is incorporated therein.
The cosmetic, dermopharmaceutical or pharmaceutical composition defined above generally comprises from 0.1% to 10%, and more particularly between 0.5% and 5%, by weight of the said reverse latex. It is, in particular, in the form of a milk, a lotion, a gel, a cream, a soap, a bubble bath, a balm, a shampoo or a conditioner.
In general, the said reverse latex can advantageously replace the products sold under the name Sepigel(trademark) 305 or Sepigel(trademark) 501 by the Applicant, in cosmetic, dermopharmaceutical or pharmaceutical compositions, since it also has good compatibility with the other excipients used for the preparation of formulations such as milks, lotions, creams, soaps, bubble baths, balms, shampoos or conditioners. It can also be used in combination with the said Sepigel products. In particular, it is compatible with the concentrates described and claimed in the international publications WO 92/06778, WO 95/04592, WO 95/13863, WO 98/47610 or FR 2 734 496, or with the surfactants described in WO 93/08204.
It is also compatible with Montanov(trademark) 68, Montanov(trademark) 82, Montanov(trademark) 202 and Sepiperl(trademark) N.
It can be used in emulsions of the type described and claimed in EP 0 629 396 and in cosmetically or physiologically acceptable aqueous dispersions with an organopolysiloxane compound chosen, for example, from those described in WO 93/05762 or in WO 93/21316. It can also be used to form cosmetically or physiologically acceptable aqueous gels at acidic pH, such as those described in WO 93/07856; it can also be used in combination with nonionic celluloses, for example to form styling gels, such as those described in EP 0 684 024, or alternatively in combination with fatty acid esters of sugars, to form compositions for treating the hair or the skin, such as those described in EP 0 603 019, or alternatively in shampoos or conditioners as described and claimed in WO 92/21316, or, finally, in combination with an anionic homopolymer such as Carbopol(trademark) or Pemulen(trademark), to form products for treating the hair, such as those described in DE 195 23596.
It is also compatible with many active principles, such as, for example, self-tanning agents such as dihydroxyacetone (DHA) or anti-acne agents; it can thus be introduced into self-tanning compositions such as those claimed in EP 0 715 845, EP 0 604 249, EP 0 576 188 or in WO 93/07902.
It is also compatible with N-acylamino acid derivatives, thereby allowing it to be used in soothing compositions, in particular for sensitive skin, such as those described or claimed in WO 92/21318, WO 94/27561 or WO 98/09611.
It is also compatible with glycolic acids, with lactic acid, with salicylic acid, retinoids, phenoxyethanol, sugars, glyceraldehyde, xanthans, fruit acids and the various polyols used in the manufacture of cosmetic formulations.
The composition according to the invention is, most particularly, compatible with cosmetic active agents that are rich in mineral salts, for example in sodium or magnesium salts. It is compatible in particular with Sepicalm(trademark) S, Sepicontrol(trademark) A5, sodium 2-pyrrolidonecarboxylate, Proteol(trademark) OAT, Ajidew(trademark) A100 or pyrrolidone.
Finally, a subject of the invention is a cosmetic, dermopharmaceutical or pharmaceutical composition as defined above and containing up to 5% by weight of one or more metal cations chosen in particular from sodium, potassium, magnesium, manganese and aluminium cations.